I had the same problem ... spilled a drink on my keyboard causing the keys to stick
1) Internet explorer browser always jumps to top of page even when trying to scroll page down
2) Windows explorer can't select any items except the top or upper most item or folder ... top item always stays selected
Fortunately, the keyboard is pretty easy to access. According to the service manual ...
1) Unplug the power cord from the wall and laptop
2) Remove the battery pack
3) Remove the lid covering the hard disk drive
4) Remove the hard disk drive and bracket assembly
5) Remove the 2 screws from the battery compartment
6) Unsnap the "Middle Cover" ... that's the small panel between the keyboard and LCD that has the power button located on it
7) The keyboard can now be gently lifted out
Download the User Manual ... SG_AS7720_7720G_BOOK.pdf ... click on the very small, almost hidden, looks like a legal disclaimer, link near the bottom of the page labeled, "Save file to your PC: click here" ...
Order a new keyboard ...
Part Name and Description
KEYBOARD 17KB-FV2 105KS WHITE US INTERNATIONAL
Acer Part No.
Google Shopping Search ... http://www.google.com/products?sourceid=navclient&rlz=1T4GGLL_en&q=Acer+Aspire+7720+Laptop+Keyboard&hl=en&um=1&ie=UTF-8&sa=N&tab=wf
Note: If you have a different model Acer laptop, here is a link to more service manuals ... http://www.acer-userforum.de/allgemein/9558-100-service-guides-anleitungen-service-manuals.html
... you can find part numbers listed in those.